A semiconductor device includes a first semiconductor chip, and a second semiconductor chip which includes a high-speed serial I/F circuit which transfers serial data between the high-speed serial I/F circuit and an external device through a serial bus and is stacked on the first semiconductor chip. A pad region in which pads (electrodes) for connecting the external device and the high-speed serial I/F circuit are disposed is provided along a first side of the second semiconductor chip which is the short side. A pad region in which pads for connecting an internal circuit included in the first semiconductor chip and the high-speed serial I/F circuit are disposed is provided along a second side of the second semiconductor chip which is the long side.